Pre-Bottling Quality Control

Pre-Bottling Quality Control
Molly Kelly
Enology Extension Specialist
Pennsylvania Winery Association
Annual Meeting
March 3, 2014
Bottling and Packaging
• One of the most critical steps in wine
• Many opportunities for problems
– People with different responsibilities
– Multiple wines to bottle
– Operation and maintenance of multiple
equipment stations
QA and QC
• Quality Assurance (QA) focuses on attempts to improve
and stabilize production practices in order to prevent
• Quality Control (QC) focuses on product testing to
uncover defects
• HACCP: means of assuring quality, through the
identification and monitoring of critical control points from
vine to glass
Pre-bottling checklist
• Chemical analysis
– Does wine meet proper criteria for bottling?
• Stability analysis
– Protein, bitartrate, color and microbiological
• Sensory analysis
• Materials
– Present and in proper condition?
Oxidation Potential
• Review your bottling system (including pre-bottling filtration) to know
the extent of oxygen pick-up
• Optimally, the oxygen pick-up during any transfer, including bottling,
=< 0.2 mg/L
• Oxidation potential can be minimized
• Particulates, case dust, adsorb air (oxygen) -increase the potential
for oxidative degradation
• The use of vacuum corkers, closure types, fill height, and the
temperature of the wine at bottling impact the oxygen pick-up
Chemical analysis
Sulfur dioxide
• The concentration of free sulfur dioxide that provides an
anti-microbiological impact is determined by the pH
• How much is based on the wine’s biological content,
wine chemistry, and how much free sulfur dioxide is lost
during your bottling operation
• Excessive oxygen pick-up during the filtration and
bottling, including lack of a vacuum system, reduces the
sulfur dioxide concentration notably
Stability Testing
• This commonly includes protein, bitartrate and
microbiological testing
• A quantitative test for L-malic acid (vs. paper
chromatography) will help assure that wines do
not undergo MLF in the bottle
• If there is a potential for Brettanomyces growth,
a biological screening should occur
Wines with malic acid
• Paper chromatography
• If malic acid is present it will be
susceptible to MLF in the bottle
• High SO2 levels at bottling and cool
storage will reduce the chances of this
• Sterile filtration can remove all bacteria
and yeast
Wines with residual sugar
• Can measure with Clinitest tablets
• Store under cool conditions (below 50F) to
avoid stimulating yeast
• Potassium sorbate can help prevent
• Not 100% effective and can impart a
bubblegum flavor to wine
Turbidity Testing
• If a wine is not brilliantly clear, it will likely plug
membrane filters
•Wines that do not clarify naturally should be tested for
pectins and/or glucans
•Polysaccharides can inhibit clarification, fining and
•Lab test: acidulated alcohol precipitation
•Use of pectolytic enzymes and/or glucanases
Sensory Evaluation
• To be a true evaluation of structural,
textural and aromatic elements, proper
serving temperature and optimal
glassware should be used
• Prior to bottling a screen for sulfur like offodors should be conducted on all wines
• Anything in contact with the wine is a
potential vector for microbial spoilage
• Have appropriate sanitation protocols in
place and implement them
Sterile bottling rooms?
• Not an absolute necessity
• Bottling area should be screened-off from
fermentation areas and excessive air
• Easily sanitized floors, walls and ceilings
Sources of contamination at
• Filter pad drip trays: drain often during runs
• Fill bowls: leaky spouts. Mist filler spouts with 70% ethanol to
inhibit microbial growth
• Corker: likely to have spilled wine so large source of
contamination. Dismantle and clean before and after. Ethanol
misting of corker jaws during bottling
• Activity: increased worker activity in bottling area increases
spread of airborne microbes. Limit number of people around
filling/corking area
Bottling Quality Control
• Wine Oxidation
– Bottling can result in 0.5 to >2.0mg of oxygen
per liter into the wine
– Impacts wine quality and shelf life
– To limit oxygen issues:
• Sulfur dioxide adds prior to bottling
• Nitrogen sparging
• Carbon dioxide or nitrogen flushing bottles before
Loss of Free Sulfur Dioxide
• Is proportional to dissolved oxygen content
• If not using vacuum fillers, corkers or flushing
bottles with gas…up to 5 ml of air in bottle head
space (750ml-1.4 mg of oxygen)
• 4 mg of sulfur dioxide are needed to neutralize
effects of 1 mg oxygen
• So an additional 5-6 mg of free SO2 is needed to
reduce oxygen in the head space
Sulfur dioxide
• Acetaldehyde formation is a direct result of oxygen
• Monitoring the free sulfur dioxide concentration could be
an effective means of reviewing the impact of different
closures and how a wine bottled with a certain closure is
holding up
• A periodic evaluation of the free sulfur dioxide level from
random bottles is an effective gauge for monitoring wine
Sulfur Dioxide
• As wines develop in the bottle and retain a level of free
sulfur dioxide exceeding 13 mg/L, the likelihood of
developing oxidized aroma/flavors is minimized
• When the free sulfur dioxide level drops to less than
about 13 mg/L, we can expect perceptible “developed”
and/or oxidative aromas
• A level of 13 mg/L or more free sulfur dioxide should be
considered an average concentration. Different wines
have differing oxidative buffering capacities (impacted by
the total antioxidant concentration)
• Antioxidants include phenols, ascorbic acid, sulfur
dioxide, etc.
• Generally, corks transported at 20o C
should be stored below 8% moisture
• Water activity is low enough to inhibit mold
• Treat corks with sulfur dioxide or purchase
treated corks
• Suppliers usually treat with SO2 gas or
ionizing radiation
Cork Questions
• Are the corks bleached?
• What is the moisture content when
• How are they sterilized?
• Do they remain sterile in your cellar?
Oxygen in the Bottle
• Can be highly variable
• When the cork is compressed in the neck of the bottle,
gas pressure in the cork cells can double, releasing
oxygen trapped in the lenticels
• In a 750-mL bottle, several tenths of a cubic centimeter
of oxygen can be released during the first weeks of
bottle aging
• How much oxygen depends on several factors: including
relative moisture content of the cork. The higher the cork
moisture, the less oxygen is released
Oxygen at Bottling
• How much is desirable, and how much is excessive?
More than 1.0 mg/L oxygen at bottling is not desirable for
any wine
• Lower concentrations are best for aromatic whites
• Red wines, due to their higher buffering capacity, can
withstand higher oxygen concentrations at bottling, up to
about 0.7 mg/L
• Factors influencing oxygen levels at bottling include wine
temperature, bottling equipment, and closure type.
• If potential for oxidation is high, do not bottle
• Increased solubility of oxygen
• High oxygen levels are especially detrimental to
wines with sorbic acid (potassium sorbate)
• Develop oxidative products that are unpleasant
Oxygen Penetration
An example of oxygen penetration in closures:
Screwcaps 0.0005 mg/L
Natural cork 0.0179 mg/L
Thus, oxygen ingress post-bottling is usually very limited,
or near zero
The exceptions include some synthetic closures
Managing oxygen ingress
• Nitrogen gas sparging pre- and/or postfilling
• Liquid nitrogen sparging pre- and/or postfilling
• Vacuum
• Most oxygen quality control strategies only
record dissolved oxygen in the wine,
leaving headspace levels unmonitored
Headspace management
• 2006-2008 International Wine Challenge in
London: almost half of wine faults were
oxygen management related
• AWRI Commercial Service and
Normacorc: bottling line audit using
PreSens® technology
PreSens technology and wine bottle
application (PreSens/Nomacorc, 2008).
Normacorc/AWRI Commercial Service
Practical winery and vineyard
Oxoluminescence technology: headspace O2 and dissolved O2
Filter integrity
• Perform frequent pressure holds
• Bubble point
• CUNO Minicheck (a 3M company)
– Hand held device
– Attach to housing and pressurize for certain
time frame
– Pass/fail
Bubble Point
The bubble point test detects minor filter defects and out-ofsize pores and correlates with the bacteria passage.
•Flood membrane with water
•Pressurize to 80% with Nitrogen gas
•Increase 2psi/min
•Note pressure when bubbling starts
and compare to filter specifications
Continuous in-line monitoring
Sample directly through
MicropreSure® monitor
via sanitary sampling
Remove excess liquid
remaining in dome with
Insert broth medium via the dome and remove excess
media with syringe. Incubate the MicropreSure® monitor.
Does not eliminate need for spot-checking bottles. Contamination can result
downstream, especially at bottle filler.
Millipore Corp.
• Logical system of control based on the
prevention of problems
Look at your process from start to finish
Decide where hazards can occur
Put in controls and monitor them
Write it all down and keep records
Ensure that it continues to work effectively
• All wineries would benefit from a basic outline
What about mobile lines?
Photo courtesy of Jennifer Foil
Thank you for your attention.
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